What can prevent a router from getting Rip packets

mason1973

Three Routers - A,B,C

B & C are working properly, but Router A appears not to be getting any Rip packets. It's routing table contains no 'R' routes.

What can prevent a router from getting Rip packets

These issues were checked and appear NOT to be the issue
-access-lists
-the interface and line connections are up
-the line protocol is up
-Rip is configured and networked properly

thanks in advance...this issue is bugging the $#@!@ out of me.

Webmaster

How are the routers connected? What type of connections?

mason1973

The routers are connected with ppp through their serial ports. The lines are up and the line protocols are up.

djjit

Router A interfaces could be in "passive" mode. Which I think prevents RIP updates??